Carbonate absorption system and process for carbon dioxide separation

Abstract

The present invention relates to systems and processes for reducing the amount of carbon dioxide in a carbon dioxide-containing gas. In particular, the carbon dioxide-containing gas is contacted with a carbonate-containing solution. At least a portion of carbon dioxide in the carbon dioxide-containing gas is absorbed in the carbonate-containing solution to produce a carbon dioxide-, carbonate-containing solution. A heat recovery mechanism is employed to recover heat from the carbon dioxide-, bicarbonate-, carbonate-containing solution exiting the chamber to maintain the temperature of the chamber within a range of from about 50° C. to about 90° C.

The invention claimed is: 
     
       1. A process for reducing the amount of carbon dioxide in a carbon dioxide-containing gas stream comprising:
 introducing said carbon dioxide-containing gas stream and a carbonate-containing solution into a chamber; 
 contacting said carbon dioxide-containing gas stream and said carbonate-containing solution in said chamber such that at least a portion of carbon dioxide from said carbon dioxide-containing gas stream is absorbed in the carbonate-containing solution; 
 converting at least a portion of said carbon dioxide and said carbonate in said carbonate-containing solution to bicarbonate to produce a carbon dioxide-, bicarbonate-, carbonate-containing solution; 
 transferring at least a portion of heat from the carbon dioxide-, bicarbonate-, carbonate-containing solution exiting the chamber to the carbonate-containing solution such that the temperature in the chamber is from about 50° C. to about 90° C.; 
 precipitating a bicarbonate-containing solid out of said carbon dioxide-, bicarbonate-, carbonate-containing solution; 
 concentrating said bicarbonate-containing solid to a bicarbonate-containing slurry; and 
 stripping said bicarbonate-containing slurry to produce a carbon dioxide product, 
 wherein the stripping is carried out in a pressurized stripping column having a pressure in the range of from 5 to 60 bar. 
 
     
     
       2. A process for reducing the amount of carbon dioxide in a flue gas stream which is generated from a fossil fuel combustion system comprising:
 introducing said flue gas stream and a carbonate-containing solution into an absorption column; 
 contacting said flue gas stream with said carbonate-containing solution in said absorption column; 
 reacting carbon dioxide in said flue gas stream with carbonate in said carbonate-containing solution to produce a carbon dioxide-, bicarbonate-, carbonate-containing solution; 
 transferring at least a portion of heat from the carbon dioxide-, bicarbonate-, carbonate-containing solution exiting the chamber to the carbonate-containing solution such that the temperature in the chamber is from about 50° C. to about 90° C.; 
 precipitating in a separating chamber a bicarbonate-containing solid out of said carbon dioxide-, bicarbonate-, carbonate-containing solution, wherein said separating chamber includes a carbon dioxide-, bicarbonate-, carbonate-containing solvent that has a solubility of bicarbonate in water that is less than the solubility in water of said carbon dioxide-, bicarbonate-, carbonate-containing solution in said absorption column; 
 concentrating said bicarbonate-containing solid to form a bicarbonate-containing slurry; 
 stripping said bicarbonate-containing slurry in a pressurized stripping column to produce a carbon dioxide product, wherein said stripping column has a pressure in the range of from 5 to 60 bar. 
 
     
     
       3. The process of  claim 2  wherein a discharge solution from the separating chamber is heated in a heat exchanging mechanism and introduced into the absorption chamber. 
     
     
       4. The process of  claim 2  wherein a carbonate-containing solution discharged from the pressurized stripping column is cooled and ultimately recycle to the absorption column. 
     
     
       5. The process of  claim 2  wherein the separating chamber further comprises a sulfate removal system.